Fungi can cause serious damage to growing or harvested crops, particularly fruit or vegetable crops. Fungicides are also used to treat fungal infections in animals.
Traditionally the principle method of control of fungi growth has been the use of synthetically produced fungicide chemicals. These synthetic fungicides frequently have high toxicity to humans and to other organisms. Because of this the use of synthetic fungicides has become more restricted due to public concern of their toxicity.
The use of naturally occurring fungicides as an alternative to synthetic chemicals is becoming more attractive due to improved biodegradation and therefore the potential for lower toxicity to both the environment and consumers of the harvested crops.
Epicoccum purpurascens (syn. E. nigrum) is a saprophytic filamentous fungi usually associated with senescing plant tissues and soil. It produces high concentrations of secondary products including a pigment that gives the media it is grown on a yellow/orange (pH dependent) colour. An orange pigment, named orevactaene was isolated from E. purpurascens and its structure described (Shu, Y. Z., et al., Bioorganic & Medicinal Chemistry Letters, 1997 7(17): p. 2295-2298; see FIG. 1). Orevactaene was found to inhibit binding of HIV-1 regulatory protein and its viral RNA binding site. It was found to have modest antifungal activity against Candidia albacans (MIC 250 μg/mL). The structure of orevactaene was determined to be that shown in FIG. 1.
Several fungal metabolites were also isolated from E. purpurascens by Kemami Wangun as described in a 2006 dissertation [Kemami Wangun, H., V, 2006, Friedrich-Schiller: University of Jena]. A yellow oil was isolated and was identified as orevactaene.
Other biologically active compounds secreted by other E. purpurascens strains have been characterised including flavipin which demonstrated antimicrobial activity against bacteria and fungi (Brown A E. et al., Soil Boil. 1987 Biochem. 19: 657-664 and Burge W R. et al., 1976 J. Agric. Food Chem. 24: 555-559), and epicoccamides (Wangun H V K. et al., 2007 J. Nat. Prod. 70: 1800-1803; Wright A D. et al., 2003 Org. Biomol. Chem. 1: 507-510) and thiornicin (Frederick C B. et al., 1981 Biochem. 20: 2436-2438) which has been demonstrated as having anti-cancer activity.
The potential use of E. purpurascens strains as a biological control for fungal growth on crops has been reported (Bhuiyan S A. et al., 2003 Plant Path. 52: 60-67; Mari M. et al., 2007 J. Sci. Food Agric. 87: 1271-1277; Szandala E S and Backhouse D 2001 Aust. Plant Path. 30: 165-170), however no demonstration of an effective control agent has been shown largely due to unsatisfactory growth and activity of the E. purpurascens strains under environmental conditions.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.